DESCRIPTION: Adds support for distributed `CREATE/DROP DATABASE `
commands from the databases where Citus is not installed
---------
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
Fixes a bug that breaks queries from non-maindbs when
citus.local_hostname is set to a value different than "localhost".
This is a very old bug doesn't cause a problem as long as Citus catalog
is available to FindWorkerNode(). And the catalog is always available
unless we're in non-main database, which might be the case on main but
not on older releases, hence not adding a `DESCRIPTION`. For this
reason, I don't see a reason to backport this.
Maybe we should totally refrain using LOCAL_HOST_NAME in all code-paths,
but not doing that in this PR as the other paths don't seem to be
breaking something that is user-facing.
```c
char *
GetAuthinfo(char *hostname, int32 port, char *user)
{
char *authinfo = NULL;
bool isLoopback = (strncmp(LOCAL_HOST_NAME, hostname, MAX_NODE_LENGTH) == 0 &&
PostPortNumber == port);
if (IsTransactionState())
{
int64 nodeId = WILDCARD_NODE_ID;
/* -1 is a special value for loopback connections (task tracker) */
if (isLoopback)
{
nodeId = LOCALHOST_NODE_ID;
}
else
{
WorkerNode *worker = FindWorkerNode(hostname, port);
if (worker != NULL)
{
nodeId = worker->nodeId;
}
}
authinfo = GetAuthinfoViaCatalog(user, nodeId);
}
return (authinfo != NULL) ? authinfo : "";
}
```
This PR makes the connections to other nodes for
`mark_object_distributed` use the same user as
`execute_command_on_remote_nodes_as_user` so they'll use the same
connection.
DESCRIPTION: Adds support for 2PC from non-Citus main databases
This PR only adds support for `CREATE USER` queries, other queries need
to be added. But it should be simple because this PR creates the
underlying structure.
Citus main database is the database where the Citus extension is
created. A non-main database is all the other databases that are in the
same node with a Citus main database.
When a `CREATE USER` query is run on a non-main database we:
1. Run `start_management_transaction` on the main database. This
function saves the outer transaction's xid (the non-main database
query's transaction id) and marks the current query as main db command.
2. Run `execute_command_on_remote_nodes_as_user("CREATE USER
<username>", <username to run the command>)` on the main database. This
function creates the users in the rest of the cluster by running the
query on the other nodes. The user on the current node is created by the
query on the outer, non-main db, query to make sure consequent commands
in the same transaction can see this user.
3. Run `mark_object_distributed` on the main database. This function
adds the user to `pg_dist_object` in all of the nodes, including the
current one.
This PR also implements transaction recovery for the queries from
non-main databases.
Halil Ozan Akgül
Onur Tirtir